• 제목/요약/키워드: Vibro-acoustic source

검색결과 27건 처리시간 0.037초

중형항공기 동체 소음해석 기법 연구 (The Study for Vibro-acoustic Noise Analysis in the Fuselage of Regional Turboprop Airplane)

  • 박일경;김성준;정진덕
    • 한국항공운항학회지
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    • 제20권3호
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    • pp.44-50
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    • 2012
  • The noise reduction is important one of considerations in the process of a civil aircraft development program. External noise sources are classified into an air-born source and a structure-born source. Among these noise sources, the most affected noise source into a cabin is the air-born noise source from an engine or propeller. The external noise is transmitted into the cabin through the fuselage structure of airplane which are composed of an fuselage structure, an interior trim panel and an acoustic insulation layer between an fuselage structure and an interior trim panel. Therefore, appropriate fuselage structure and acoustic insulation layer is very important to reduce the internal noise level. In this paper, the vibro-acoustic coupled analysis of the cabin noise of the 80~90 seats regional turboprop aircraft is carried out to validate the acoustic analysis method using Direct BEM and FEM. The sound pressure level onto the fuselage skin is acquired by fan-source noise analysis using BEM, and which sound pressure is used as acoustic noise source in vibro-acoustic noise analysis for cabin noise analysis using FEM.

NEW TECHNIQUE IN THE USE OF VIBRO-ACOUSTICAL RECIPROCITY WITH APPLICATION TO THE NOISE TRANSFER FUNCTION MEASUREMENT

  • Ko, K.H.;Kook, H.S.;Heo, S.J.
    • International Journal of Automotive Technology
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    • 제7권2호
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    • pp.173-177
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    • 2006
  • A noise transfer function(NTF) is the frequency response function between an input force applied to an exterior point of a vehicle body and the resultant interior sound pressure usually measured at the driver's ear position. It represents the measure of noise sensitivity for the output force transmitted to the joints between the body and chassis. The principle of vibro-acoustic reciprocity is often utilized in the measurement of NTF. One difficulty in using the volume source is that most of the previously proposed methods require the knowledge of the volume velocity of the acoustic source in advance. A new method proposed in the present work does not require any calculation related with the volume velocity of the acoustic source, but still yields even more accurate results both in the amplitude and phase of the NTF. In the present work, the new method is applied to obtain NTF data for a midsize sedan.

EXPERIMENTAL IDENTIFICATION ON A GEAR WHINE NOISE IN THE AXLE SYSTEM OF A PASSENGER VAN

  • Kim, S.J.;Lee, S.K.
    • International Journal of Automotive Technology
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    • 제8권1호
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    • pp.75-82
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    • 2007
  • This paper presents practical work on the reduction of gear whine noise. In order to identify the source of the gear whine noise, transfer paths are searched and analyzed by operational deflection shape analysis and experimental modal analysis. It was found that gear whine noise has an air-borne noise path instead of structure-borne noise path. The main sources of air-borne noise were the two global modes caused by the resonance of an axle system. These modes created a vibro-acoustic noise problem. Vibro-acoustic noise can be reduced by controlling the vibration of the noise source. The vibration of noise source is controlled by the modification of structure to avoid the resonance or to reduce the excitation force. In the study, the excitation force of the axle system is attenuated by changing the tooth profile of the hypoid gear. The modification of the tooth profile yields a reduction of transmission error, which is correlated to the gear whine noise. Finally, whine noise is reduced by 10 dBA.

구조가진과 음향 가진의 결합에 의한 차량의 구조-음향 전달 함수 측정 (Measurement of Mechanical-acoustic Transfer Functions of Vehicles by Combination of Mechanical and Acoustic Excitations)

  • 고강호;이장무
    • 한국자동차공학회논문집
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    • 제7권9호
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    • pp.158-164
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    • 1999
  • In this paper a simple measurement technique for mechanical-acoustic transfer functions is proposed . The mechanical-acoustic transfer functions, generally , are measured through mechanical excitations ; impact hammers or shakers. Recently , by virtue of vibro-acoustical reciprocity principle, they are measured through acoustic excitations : loudspeakers. This kind of test needs to measure the volume velocity , the radiation characteristics of a sound source. Because the volume velocity of the sound source is changed by driving signal , it is difficult to measure it. However , the new method in this paper needs not to measure the volume velocity of a sound source by combination of mechanical and acoustic excitations. Moreover, this method has the methodological advantages, such as usage of a general loudspeaker for the reciprocal excitation, no sptatial limitations for measurements of mechanical-acoustic transfer functions.

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위성 발사체 페어링 내부음향 해석 (Acoustic Analysis in the Payload Fairing of Launch Vehicle)

  • 서상현;박순홍;정호경;장영순
    • 한국소음진동공학회논문집
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    • 제21권12호
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    • pp.1146-1151
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

위성 발사체 페어링 내부음향 해석 (Acoustic Analysis in the Payload Fairing of Launch Vehicle)

  • 서상현;박순홍;정호경;장영순
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2011년도 추계학술대회 논문집
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    • pp.196-201
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

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진동-음향 상반 원리에 이용되는 음원의 유효 면적 측정 (The Application of Equivalent Area to the Volume Velocity for Using the Vibro-acoustical Reciprocity)

  • 고강호
    • 소음진동
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    • 제9권5호
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    • pp.943-948
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    • 1999
  • This paper proposes a feasible and effective method for measuring the mechanical-acoustic transfer function by the application of equivalent area and velocity transfer function, a manifestation of the vibro-acoustical reciprocity principle. On the contrary to the volume velocity used in traditional method, the equivalent area is a peculiar raidation characteristics of sound sources and not influenced by any input signal for driving sound source. This invariant property of equivalent area can get rid of boresome works to measure the volume velocity of a sound source every time the driving signal is changed. Moreover, this method has a remarkable advantage to use a general loudspeaker as an accoustic exciter without the assumption of point source and can be applied to all kinds of sound sources even if they are not omni-directional sources.

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구조-음향 상반성 원리를 이용한 공기기인 소음원의 강도 추정 및 소음 합성 (The Use of Vibro-acoustical Reciprocity to Estimate Source Strength and Airborne Noise Synthesis)

  • 김윤재;변재환;강연준;홍진철;권오준;강구태
    • 한국소음진동공학회논문집
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    • 제19권1호
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    • pp.42-49
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    • 2009
  • In this paper, an alternative method was introduced to conduct a transfer path analysis for airborne noise. The method used the transfer function matrix composed of acoustic transfer functions that are referenced by the input voltage of a calibration source. A calibration factor which is converting a virtual voltage to source strength was deduced by vibro-acoustical reciprocity theorem. The calibration factor is then multiplied to the virtual input voltage to estimate the operational source strength. Three loudspeakers were used to noise sources of acrylic half car model. The method was applied to airborne noise transfer path analysis of the half car. The estimated source strength by transfer path analysis was compared the deduced source strength by vibro-acoustical reciprocity to verify the method.

구조 방사 소음의 해석을 위한 구조물의 진동 획득 방법의 비교 (Comparison of various methods to obtain structural vibration for vibro-acoustic noise)

  • 왕세명;신민철;구건모;김대성;배원기;경용수;김정선;국정환
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2006년도 추계학술대회논문집
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    • pp.607-611
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    • 2006
  • There are several methods to obtain structural vibration for analysis of vibro-acoustic noise. First of all, vibration data can be obtained through the structural analysis using finite element method. Although this method has no need to experiment, the analysis result is unreliable when the structure and the vibration source is complex to model exactly. The second method is to measure vibration using a number of sensors. The analyzed vibro-acoustic noise with directly measured data is setting morereliable when the number of data acquisition points is getting larger. However, it requires large amount of time and effort to measure all vibration data on every node especially when the size of vibrating structure is large. The Modal Expansion Method(MEM), which uses mode information and measurement data, has been introduced to compensate their limits. With a relatively small number of measurement data, the reliable structural vibration for vibro-acoustic noise can be obtained using this semi-analysis method. Although MEM gives reliable result, it is restricted by the number of modes and measurement points. In this paper, structural analysis, direct vibration measurement method and MEM are compared using the simple aluminum box model. Furthermore, the washing machine case is also provided as a comparative example. The Laser Doppler Vibrometer(LDV) was used instead of contact type accelerometer to get vibration data.

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파워흐름해석법을 이용한 중고주파수 대역 소음해석 프로그램 개발 (Development of Noise Analysis Program by using Power Flow Analysis in Medium-to-high Frequency Ranges)

  • 권현웅;송지훈;홍석윤
    • 대한조선학회논문집
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    • 제49권5호
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    • pp.384-390
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    • 2012
  • Power Flow Analysis (PFA) is introduced for solving the noise and vibration analysis of structures in medium-to-high frequency ranges. The vibration analysis software, $PFADS_{C{+}{+}}$ R4 based on Power Flow Finite Element Method (PFFEM) and the noise prediction software, $NASPFA_{C{+}{+}}$ R1 based on Power Flow Boundary Element Method (PFBEM) are developed. In this paper, the coupling equation which represents relation between structural energy and acoustic energy is developed for vibro-acoustic coupling analysis. And vibro-acoustic coupling analysis software based on PFA and coupling equation is developed. Developed software is composed of translator, cavity-finder, solver and post-processor over all. Translator can translate FE model into PFADS FE model and cavity-finder can automatically make NASPFA BE model from PFADS FE model for noise analysis. The solver module calculates the structural energy density, intensity of structures, the fictitious source on the boundary and the acoustic energy density at the field in acoustic cavities. Some applications of vibro-acoustic coupling analysis software to various structures and cruise ship are shown with reliable results.